Servers are loud because they are loaded with cooling fans that pump as much air through them as possible. Sound is measured in Bels or the more common unit decibels, which is 10 Bels. The Bel is measured on a logarithmic scale. An increase in 3dB approximately doubles the volume. This acoustic measurement was originally developed by the Bell Telephone Company and quantified the signal loss of a telephone transmission over 1 mile of cable. Bell Telephone came up with the measurement so they had the privilege of naming it after the founder of the company, Alexander Graham Bell.
Not surprisingly there are a number of complaints about the Acoustic Noise Emission of today’s servers. The manufacturer’s have tried all kinds of firmware modifications that will run the cooling fans at the absolute minimum speed to keep the equipment cool. If the acoustical noise emission of a server must be reduced to a minimum then there are special Acoustic Server Racks that do this very well.